physical chemistry

These are my favorite lines out of all the books I have read. They are from Atkins and de Paula’s “Physical Chemistry” book, Reaction Dynamics Chapter. The book is a fascinating read (for physical chemistry students and instructors), it is easily accessible and these lines make it high literature. By the time you get to this chapter, you have discussed equilibrium thermodynamics, statistical mechanics and you have started thinking about molecules, why they behave the way do and how their molecular behavior results in properties you observe in the macroscopic world. But you have not gotten to the heart, yet.

My favorite teaching moment is when I say these lines in class. Students have come in, I have waited for them to settle, I have made eye contact with several of them that are waiting for their friends to be quiet. I say “Now we are at the heart of chemistry” and pause for dramatic effect. I know some eyes roll. But some of the students are intrigued. “Can you imagine being at the HEART of CHEMISTRY?”. I remind them of the energy levels, the partition function (“what was that?” “the number of accessible energy states”) and tell them that knowing the partition function will let us know whether two molecules will react or not. That knowledge is powerful. It takes us from single molecules, “bonds being ripped apart” to all the reactions we see around us and to life. Transition state theory, which explains reaction mechanisms, is one of the hardest topics to grasp in physical chemistry. But, I remind you, it takes us to the heart and once you get to the heart it is almost like magic except that it is all rooted in theory.